This invention relates to a direct injected engine and more particularly to an improved feedback control system and sensor positioning arrangement for a direct injected, two-cycle, internal combustion engine.
The advantages of two-cycle engines insofar as simplicity and high specific output are well-known. However, because of the scavenging system of such engines, it frequently is difficult to control the emission of constituents such as hydrocarbons. That is, in order to ensure good scavenging and high performance, it is frequently the case that fuel passes out of the exhaust port and gives rise to these problems. This characteristic is a result of the fact that the scavenging of the engine takes place during the end of the expansion stroke because of the fact that this type of engine fires every revolution of the crankshaft.
In order to provide more efficient emission control and better performance for two-cycle engines, it has been proposed to utilize either or both of direct cylinder fuel injection and feedback control using combustion condition sensors such as oxygen (O.sub.2) sensors. Direct fuel injection permits more accurate control of the amount of fuel that is introduced into the cylinder and permits adjustment on a cycle-to-cycle basis. Oxygen or feedback control systems, permit relatively instantaneous response to variations from the desired air fuel ratio.
The problems with the combination of these two methodologies i.e., utilizing direct cylinder injection and feedback control is that the fuel sprayed by the injector may impinge upon the sensor and give erroneous readings. Thus, it is important that the sensor be located in such a way that it retains a representative sample of the combustion products and that it does not receive the direct spray of fuel from the injector.
It is, therefore, a principal object of this invention to provide an improved direct injected two-cycle internal combustion engine having feedback control.
It is a further object of this invention to provide an improved sensor-positioning arrangement for a two-cycle direct cylinder injected engine.